Short answer. At the same time as the lease of the unit itself. Article 1688 provides that when a landlord who leases a dwelling, store, or industrial establishment also leases the furniture in it, the lease of that furniture is deemed to run for the same duration as the lease of the premises.
What the law says
When the lessor of a house, or part thereof, used as a dwelling for a family, or when the lessor of a store, or industrial establishment, also leases the furniture, the lease of the latter shall be deemed to be for the duration of the lease of the premises.
Civil Code, Article 1688 — Lease of Furniture With the Premises. Read the full provision →
One duration for the unit and its furniture
Article 1688 removes any need to track two separate timelines for a furnished lease. It provides that when the lessor of a house, or part thereof, used as a dwelling for a family, or when the lessor of a store, or industrial establishment, also leases the furniture, the lease of the latter shall be deemed to be for the duration of the lease of the premises. Because your landlord leased both the dwelling and the furniture inside it, the law treats the furniture lease as bound to the same term as the lease of the unit itself, rather than as a separate arrangement that could expire on its own schedule.
This covers dwellings as well as commercial spaces
The article is not limited to residential units. It applies equally where the leased space is a house or part of a house used as a family dwelling, and where it is a store or an industrial establishment, as long as the landlord is also the one leasing out the furniture along with the space. Whether you rented a furnished apartment to live in, or a furnished shop or workspace, the same rule ties the furniture's lease term to the term of the space it sits in.
Why the law links the two together
Furniture supplied along with a leased space is ordinarily part of what makes the unit usable for its intended purpose, whether that is a livable family home or a functioning store. Treating the furniture as having its own, potentially different, lease period would create unnecessary complications, such as the furniture lease ending mid-tenancy while the space lease continues, or vice versa. Tying both to a single duration keeps the arrangement coherent and avoids that mismatch.
What this means for your furnished rental
Because your landlord leased the furniture together with the dwelling, you do not need a separate agreement or a separate expiration date to know when your right to use the furniture ends: it ends exactly when your lease of the unit itself ends. If you and the landlord want the furniture's terms to genuinely differ from the lease of the premises, that would need to be addressed specifically, since the default rule ties the two together.